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MG TD TF 1500 - Vapor Lock?

So today I'm driving the TD to keep it limber, and when I return and let the car sit 15-20 min in the garage, it won't start without the choke and runs rough. Pull the choke, and it starts, and blipping the throttle a few times, and it clears up and idles fine. Engine temp had risen to 92F in the garage when I re-started. I'm thinking vapor lock, and I believe I have been here before, but just wanted to confirm. All comments appreciated.
L Karpman

Sure sounds like VL
Are you dure that it is 92F ?? Thats pretty low! VP would.be at a much higher temp.

Steve
Steve Wincze

92C would be 196F , which is more like a VL range
Steve Wincze

Steve, I meant 92C. Sorry.
L Karpman

Mine has vapor locked here in the central Texas heat more than once, just as you describe. Choke, run it a bit and all is well.

BobbyG
Bobby Galvez

One thing to check,, how close are your fuel bowls to the exhaust manifold??? can you rotate them a bit further away from the manifold?? I'll post a picture tomorrow.

Steve
Steve Wincze

Larry,
Here is the pic of the distance between the float bowl and the hot exhaust manifold,,
The closer the bowl is to the manifold, the more heat it will pick up.

Thanks for the picture Dave!

Steve


Steve Wincze

I wouldn't think vapor lock would be a problem in the float bowls. If the fuel started to evaporate in the bowl the float would drop and the fuel pump would immediately send more, cooler fuel to the bowl. I've seen vapor lock more often in fuel lines.

Tim
TD12524
TW Burchfield


This certainly sounds similar to the problem I had and that was subsequently cured by installing a heat shield.

It is odd that this issue is now apparent in your car - I would have thought the issue would have been around on hot days before.

I always get suspicious of the coil though when the engine stumbles when hot...so there is a small chance it could be that instead. A quick swap with a known working coil will confirm or not.

Doctor Bob

Sift through the archives. This topic has been covered in great detail over the years, with many successful cures. George
George Butz

"It is odd that this issue is now apparent in your car - I would have thought the issue would have been around on hot days before."

Thanks Doctor Bob. As I said in my original post, "I believe I have been here before, but just wanted to confirm." (vapor lock)

I've scanned the archives, and yes, there has been success with heat shields, and no success with heat shields too. I'll go back and scan some more, but personally I don't mind having to pull the choke and blip the throttle a few times after being shut down for 10-15 minutes. If shut down longer, car starts just fine on first try.
L Karpman

Larry,

You aren't broke so don't fix it. If you car starts fine the first time you start for the day, and you have choke and blip after resting for 10 to 15 minutes on a hot day, you're typical - maybe even better than most since you say it runs well after that.

Of course...you could install a supercharger....

Gene
Gene Gillam

"Of course...you could install a supercharger...."

Ha, I'd probably blow the TD up with one. I haven't driven the car that much in the last few years due to playing with doctors and surgeons for a new hobby.

Recently (this spring) had the carbs rebuilt by Dave Braun, finally installed that Jet-Hot coated exhaust manifold you handled for me 6 or 7 years ago, and added a new stainless exhaust system, as well as new bushings all around.

I was surprised that it ran at 90C on an 85F day though. I was pretty sure my issue was vapor lock, but as it had been so long since I experienced it last, I thought I'd ask to confirm.

I'd would like to get the running temp down though. I'm sure my radiator could stand a rebuild or at least a flush, but I'm going to start with adding some Water Wetter, as it's been years since I used some, and I have no idea how long that stuff is supposed to last.
L Karpman

Heat shield. Quite easy and was one of my steps to happiness and joy. A supermarket cookie sheet gave it's life.


Don't overlook the exhaust system. I had a Midas POS from the 80's lovingly installed by a PO. Factory spec in stainless... breathing much easier, cooler.

...


MAndrus

Don't overlook the exhaust system. I had a Midas POS from the 80's lovingly installed by a PO. Factory spec in stainless... breathing much easier, cooler.

The exhaust is a new Bell Stainless system. Thanks for the diagram and pic.
L Karpman

I have just ordered a heat shield from Barrie Jones for my '55 TF 1500. It is in the mail so I have not had chance to see the results. Currently my normal temperature when cruising at 45 mph is around 175 with an ambient of 85F in the shade but the car exposed to full sun. When I switch off and park the heat soak moves the temperature gage to 200F. Engine will not restart at that gage reading. Opening the hood and allowing indicated reading to drop to 180 the engine starts without a problem

I have also purchased a late MGB 7 bladed plastic fan that I have not had time to fit to increase airflow through the engine compartment to reduce the heat build up standing in traffic

The original TF shown to the Board for production approval had louvres in the TF hood but these were removed in the production version. I am toying with making a duplicate hood with louvres to see how they allow the heat build up to dissipate. I don't want to modify my existing hood as the car is close to the original build. I do not wish to add an electric fan as I am still positive ground and the old style generator may not be able to hack it in stop/go traffic

Obviously the heat shield and MGB fan are off standard but temperatures here in Florida are much higher than the cold and wet TF country of origin

Hopefully I will have the updates in place before the cool weather and will report on the results

PS Anyone have a TF hood they wish to part with for a reasonable price for my louvre experiment?
I Massey

A heat shield will do NO good for the circumstance described.. That being heat soaking of the entire engine compartment when the car sits for 15-20 minutes after a run. A properly tuned, normally aspirated Td/Tf will not vapor lock while running.
Regards, tom
tm peterson

Just a tip! I installed a Barrie Jones heat shield on the TF and thought I'd give a report on how well it works. Hardly no improvement at all if installed out of the box. It's stainless steel and looks pretty when installed, but it needs to be insulated on the back side to work properly. Being stainless steel, it transfers heat directly through it to the carbs. Say what you will and do as you wish, but I'm pulling the heat shield off and riveting high temp insulation to the back side of the plate, a little like how the MGB shields came through, only they used asbestos. If your going to make your own, make it out of aluminum, less heat transfer than steel, steel has zero insulating qualities. PJ
Paul161

Paul161 - Thanks for the tip, it makes sense and as I have not installed the heat shield yet I can easily add the insulation you suggest

TM Peterson - my thoughts also but I figured the 7 bladed MG B fan will blast more air through and the steel heat shield will transfer more heat to the cooling air from the fan to make cooling more effective in standing traffic. I have never had a vapor lock with the engine running

As I don't wish to add an electric fan due to using the original generator, which may not be up to keeping the battery charge healthy in stop/go traffic, I like the idea of the louvres in the hood. They will allow the heat to escape rather than build up under the hood. Positioning will be critical under running conditions. Unfortunately they dropped this feature when they placed the TF into final production. At least I will be able to claim that my TF reflects the original prototype shown to the board for production approval ;-)
I Massey

It is vapour lock. Ethanol boils at 86C and your gas contains ethanol. You need to fit a heat shield between exhaust manifold and carb float chambers. I make one for the TF but unfortunately it will not fit a TD with the original air intake system.
B T Jones

You might try wrapping the float bowls with some foam home pipe insulation holding it on with some nylon wire ties as a test. Easy to do and completely reversible.
You can also cover the metal fuel lines in the engine bay leading to the fuel pump with some rubber hose or aquarium hose split down the middle.
John Quilter (TD8986)

Barrie - here in the USA some of us have access to Ethanol-free gas. For example, several filling stations where I live in Florida have an Ethanol-free gas pump primarily for the boat owning fraternity. I always use Ethanol-free gas in my TF so no Ethanol in my gasoline

A number of other classic car owners I know go for Ethanol-free gas as it is readily available locally
I Massey

I use Ethanol free gas in the TF. Closest station to me is a Conoco and all their regular gas is Ethanol free. Louvers were quite popular in the day. PJ




Paul161

This thread was discussed between 13/09/2015 and 22/09/2015

MG TD TF 1500 index

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